Colombia's Marxist FARC rebel group will officially launch its new political party on Sept. 1, part of a peace deal with the government under which former guerrilla fighters will serve in congress.

The Revolutionary Armed Forces of Colombia (FARC) fought the government for more than half a century, but handed in its weapons as part of a deal negotiated during more than four years of talks in Cuba.

"From Sept. 1 we will be publicly launching our new political movement" said FARC secretariat member Carlos Antonio Lozada. The launch will be celebrated at an event outside of Congress in Bogota's Bolivar Plaza.

The accord allows the FARC 10 unelected seats in Congress through 2026 and grants amnesty to the majority of ex-fighters.

Rebels convicted by special courts of human rights violations will avoid traditional prison sentences, instead performing reparations work such as removing landmines.

A rebel of the Revolutionary Armed Forces of Colombia, FARC, waves a white peace flag during an act to commemorate the completion of their disarmament process in Buenavista, Colombia, June 27, 2017.

The group has not yet announced which of its members will fill the congressional seats or the new party's name, but will hold meetings before the launch to fine-tune its policy proposals, Lozada said.

"In the coming days we will focus on not just the names but above all and fundamentally the proposals," he added.